首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   996篇
  免费   41篇
  国内免费   16篇
化学   524篇
晶体学   6篇
力学   49篇
数学   177篇
物理学   297篇
  2023年   10篇
  2022年   13篇
  2021年   18篇
  2020年   19篇
  2019年   24篇
  2018年   26篇
  2017年   27篇
  2016年   30篇
  2015年   37篇
  2014年   44篇
  2013年   82篇
  2012年   79篇
  2011年   81篇
  2010年   58篇
  2009年   35篇
  2008年   63篇
  2007年   52篇
  2006年   37篇
  2005年   24篇
  2004年   23篇
  2003年   12篇
  2002年   19篇
  2001年   16篇
  2000年   13篇
  1999年   6篇
  1998年   8篇
  1997年   5篇
  1996年   5篇
  1995年   11篇
  1994年   11篇
  1993年   8篇
  1992年   6篇
  1991年   8篇
  1990年   11篇
  1989年   5篇
  1987年   5篇
  1985年   11篇
  1984年   12篇
  1983年   12篇
  1982年   5篇
  1981年   13篇
  1980年   4篇
  1979年   4篇
  1978年   4篇
  1976年   4篇
  1974年   4篇
  1972年   4篇
  1968年   4篇
  1956年   5篇
  1954年   6篇
排序方式: 共有1053条查询结果,搜索用时 31 毫秒
71.
Experimental measurements of rovibrational product state distributions for the inelastic scattering process H + D2(nu=0,j)-->H + D2(nu' = 1,2,j') are presented and compared with the results of quasiclassical and quantum mechanical calculations. Agreement between theory and experiment is almost quantitative. Two subtle trends are found: the relative amount of energy in product rotational excitation decreases slightly with increasing collision energy and increases slightly with increasing product vibrational excitation. These trends are the reverse of what has been found for reactive scattering in which the opposite trends are much more pronounced.  相似文献   
72.
The absolute value of the cross section for the abstraction reaction between fast H atoms and H2O has been determined experimentally at a mean collision energy of 2.46 eV. The OH population distribution at the same mean energy has also been determined. The new measurements are compared with state-of-the-art quantum mechanical and quasiclassical scattering calculations on the most recently developed potential energy surface.  相似文献   
73.
We propose commutation relations for a single mode -deformed para-Bose oscillator. In this new deformation of para-Bose statistics the distribution function has the same form as in the para-Bose statistics. Furthermore, we show analogies between the coherent states of -deformed and q-deformed para-Bose statistics.  相似文献   
74.
Experimental arrangement consisting of spontaneous parametric down converter with type-I phase matching (SPDCI) and a beam splitter with unitary Hadamard transformation is proposed for conditional preparation of macroscopic entangled states. The given method requires no photon number resolving detection to generate most probable macroscopic entangled state. We calculate the amount of entanglement stored in the macroscopic entangled states and develop a method to increase the amount of entanglement stored in the state.  相似文献   
75.
This work describes a novel type of working electrode for use in voltammetry and polarography — the renewable silver liquid amalgam film–modified silver solid amalgam annular band electrode (AgLAF–AgSAE). The electrode is produced by mechanically refreshing the silver liquid amalgam film (AgLAF) before each measurement. The main constituents of the electrode are: a specially constructed silver solid amalgam annular band electrode (AgSAE), two silicon O-rings, silver liquid amalgam and a polypropylene electrode body. Contaminants from the analyzed solution are removed and the AgSAE surface is covered with a thick layer of fresh amalgam while pulling the AgSAE into the sensor body. During movement in the reverse direction AgLAF is formed and homogenized. The time needed to refresh the film is less than 1 s. The electrode is characterized by excellent surface repeatability (~ 1%) and long-term stability (over ten thousand measurement cycles).  相似文献   
76.
We develop a method for adaptive mesh refinement for steady state problems that arise in the numerical solution of Cahn–Hilliard equations with an obstacle free energy. The problem is discretized in time by the backward-Euler method and in space by linear finite elements. The adaptive mesh refinement is performed using residual based a posteriori estimates; the time step is adapted using a heuristic criterion. We describe the space–time adaptive algorithm and present numerical experiments in two and three space dimensions that demonstrate the usefulness of our approach.  相似文献   
77.
A theoretical approach to polycondensation reaction of Aa-Bb type Involving intramolecular cycllzatlon has been proposed by Tang Au-chin et al.. In this paper, the theoretical sol-gel distribution is tested by polycondensation of adipic acid with trimethylol propane in a sto-ichiometric ratio of 0. 8, and the effect of intramolecular cyclization is discussed in detail.  相似文献   
78.
In this study, electron paramagnetic resonance of γ-irradiated single crystals of N-Trifluoroacetyl-α-amino isobutyric acid (F3Ac-Aib-OH) was investigated at room temperature and analyzed for different orientations of the crystal in the magnetic field. The paramagnetic species in N-Trifluoroacetyl-α-aminoisobutyric acid was attributed to the ?F2-R radical (R= CONHC(CH3)COOH). Hyperfine coupling constants and g value were also determined. In addition, the single crystal of F3Ac-Aib-OH was UV-irradiated and paramagnetic species formed was studied at room temperature. The effects of gamma irradiation on fluoroamino acid and stability were discussed.  相似文献   
79.
80.
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号